Person: Fernández Pérez, Luis Antonio
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First Name
Luis Antonio
Last Name
Fernández Pérez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física Teórica
Area
Física Teórica
Identifiers
4 results
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Item Spin-glass dynamics in the presence of a magnetic field: exploration of microscopic properties(Journal of statistical mechanics: theory and experiment, 2021) Paga, I.; Zhai, Q.; Baity-Jesi, M.; Calore, E.; Cruz, A.; Fernández Pérez, Luis Antonio; Gil-Narvión, J. M.; González-Adalid Pemartín, Isidoro; Gordillo Guerrero, A.; Iñiguez, D.; Maiorano, A.; Marinari, E.; Martín Mayor, Víctor; Moreno Gordo, J.; Muñoz Sudupe, Antonio; Navarro, D.; Orbach, R. L.; Parisi, G.; Perez-Gaviro, S.; Ricci-Tersenghi, F.; Ruiz-Lorenzo, J. J.; Schifano, S. F.; Schlagel, D. L.; Seoane Bartolomé, Beatriz; Tarancón, A.; Tripiccione, R.; Yllanes, D.The synergy between experiment, theory, and simulations enables a microscopic analysis of spin-glass dynamics in a magnetic field in the vicinity of and below the spin-glass transition temperature T-g. The spin-glass correlation length, xi(t, t(w); T), is analysed both in experiments and in simulations in terms of the waiting time t(w) after the spin glass has been cooled down to a stabilised measuring temperature T < T-g and of the time t after the magnetic field is changed. This correlation length is extracted experimentally for a CuMn 6 at. % single crystal, as well as for simulations on the Janus II special-purpose supercomputer, the latter with time and length scales comparable to experiment. The non-linear magnetic susceptibility is reported from experiment and simulations, using xi(t, t(w); T) as the scaling variable. Previous experiments are reanalysed, and disagreements about the nature of the Zeeman energy are resolved. The growth of the spin-glass magnetisation in zero-field magnetisation experiments, M-ZFC(t, t(w); T), is measured from simulations, verifying the scaling relationships in the dynamical or non-equilibrium regime. Our preliminary search for the de Almeida-Thouless line in D = 3 is discussed.Item Numerical test of the replica-symmetric Hamiltonian for correlations of the critical state of spin glasses in a field(Physical review E, 2022) Fernández Pérez, Luis Antonio; González-Adalid Pemartín, Isidoro; Martín Mayor, Víctor; Parisi, G.; Ricci-Tersenghi, F.; Rizzo, T.; Ruiz Lorenzo, J. J.; Veca, M.A growing body of evidence indicates that the sluggish low-temperature dynamics of glass formers (e.g., supercooled liquids, colloids, or spin glasses) is due to a growing correlation length. Which is the effective field theory that describes these correlations? The natural field theory was drastically simplified by Bray and Roberts in 1980. More than 40 years later, we confirm the tenets of Bray and Roberts’s theory by studying the Ising spin glass in an externally applied magnetic field, both in four spatial dimensions (data obtained from the Janus collaboration) and on the Bethe lattice.Item Scaling Law describes the spin-glass response in theory, experiments, and simulations(Physical review letters, 2020) Paga, I; Fernández Pérez, Luis Antonio; González-Adalid Pemartín, Isidoro; Martín Mayor, Víctor; Muñoz Sudupe, Antonio; Seoane Bartolomé, Beatriz; otros, ...The correlation length xi, a key quantity in glassy dynamics, can now be precisely measured for spin glasses both in experiments and in simulations. However, known analysis methods lead to discrepancies either for large external fields or close to the glass temperature. We solve this problem by introducing a scaling law that takes into account both the magnetic field and the time-dependent spin-glass correlation length. The scaling law is successfully tested against experimental measurements in a CuMn single crystal and against large-scale simulations on the Janus II dedicated computer.Item Temperature chaos is present in off-equilibrium spin-glass dynamics(Communications physics, 2021) Fernández Pérez, Luis Antonio; González-Adalid Pemartín, Isidoro; Martín Mayor, Víctor; Muñoz Sudupe, Antonio; Seoane Bartolomé, Beatriz; otros, ...Experiments featuring non-equilibrium glassy dynamics under temperature changes still await interpretation. There is a widespread feeling that temperature chaos (an extreme sensitivity of the glass to temperature changes) should play a major role but, up to now, this phenomenon has been investigated solely under equilibrium conditions. In fact, the very existence of a chaotic effect in the non-equilibrium dynamics is yet to be established. In this article, we tackle this problem through a large simulation of the 3D Edwards-Anderson model, carried out on the Janus II supercomputer. We find a dynamic effect that closely parallels equilibrium temperature chaos. This dynamic temperature-chaos effect is spatially heterogeneous to a large degree and turns out to be controlled by the spin-glass coherence length xi. Indeed, an emerging length-scale xi* rules the crossover from weak (at xi MUCH LESS-THAN xi*) to strong chaos (xi >> xi*). Extrapolations of xi* to relevant experimental conditions are provided. While temperature chaos is an equilibrium notion that denotes the extreme fragility of the glassy phase with respect to temperature changes, it remains unclear whether it is present in non-equilibrium dynamics. Here the authors use the Janus II supercomputer to prove the existence of dynamic temperature chaos, a nonequilibrium phenomenon that closely mimics equilibrium temperature chaos.